Male infertility caused by primary testicular failure is enigmatic as to etiology, diagnosis, and treatment. This situation is intimately related to the current lack of knowledge concerning hormonal requirements for spermatogenesis. In the proposed studies, genetically defined male-sterile mutant mice provide a unique approach to a comprehensive investigation of male infertility. I plan to exploit these mice to decipher steroid hormonal requirements for spermatogenesis. The primary hypothesis to be tested is steroid hormonal requirements for spermatogenesis can be determined by defining and correlating the defects in spermatogenesis and steroidogenesis which occur in mutant mice. The validation of a technique for the in vitro perfusion of mouse testes was a critical step in developing the experiments to test this hypothesis. Testes perfused in vitro provide for two factors that may be crucial for normal steroid metabolism: 1) the maintenance of intercellular relationshps and 2) endogenously produced steroids. In vitro perfusion and quantitative histological examination of testes from mutant mice and their normal siblings will be used to identify and relate specific defects in steroidogenesis and spermatogenesis (gas chromotography will be used to quantitate steroids secreted by in vitgro perfused testes). This new information will be applied in the development of diagnostic and therapeutic procedures. Various methods for the study of steroid metabolism in human testicular biopsy specimens will be investigated. The quantitative determination of a tissue's capability for steroid metabolism is required if the new knowledge resulting from the proposed studies is to be used for precise diagnosis of male infertility. A third part of the proposed investigation entails the testing of therapies based on the correlation of steroidogenic alterations and specific spermatogenic errors. This practical application will involve intratesticular pellets containing steroids identified as parameters for specific failures in spermatogenesis. together, these studies of the etiology, diagnosis, and treatment of male infertility will elucidate the role that steroids have in normal spermatogenesis and consequently improve the prognosis of male infertility. Although this investigation focuses on testicular steroids, it represents only one aspect of male infertility that can be explored using the genetically defined mouse models of male infertility.